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Medical Minute 10-14: Suffocating Damaged Nerves Back to Life

By: Andrew McIntosh Email
By: Andrew McIntosh Email

27-year-old Drew Durrence is all about overcoming challenges. Eight years ago, he injured his spinal cord in a dirt bike accident.

"When I tried to get up, I lost feeling and movement from about chest down," said Drew Durrence.

Therapy-- and Drew's determination -- have brought some of that back. Now, he's part of a unique trial.

Physical therapist and biomedical engineer Doctor Randy Trumbower is studying how oxygen deprivation can trigger molecular changes that excite -- or wake up -- the nervous system.

"And so what we're hoping is that by intermittently stimulating the spinal cord with this type of breathing intervention, that we're actually turning up the volume on spared connections," said Randy Trumbower, Ph.D., Assistant Professor, Rehabilitation Medicine Emory University School of Medicine.

Patients alternately breathe air with low, nine percent oxygen and normal, 21 percent oxygen.

"We found that individuals that experienced intermittent hypoxia for one day, for 45 minutes of exposure actually increased, on average, 80 percent changes in strength."

In early trials, this oxygen deprivation therapy also helped patients use muscles they couldn't use before.

"If you can get just a little bit more strength where it makes it easier for you to stand up, or easier for you to do something, that's just another step."

Whatever it takes, Drew says he'll keep challenging himself to do more -- taking control of his injury, instead of letting it control him.

For more information on other series produced by Ivanhoe Broadcast News contact John Cherry at (407) 691-1500, jcherry@ivanhoe.com.

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MEDICAL BREAKTHROUGHS - RESEARCH SUMMARY:

BACKGROUND: A spinal cord injury often causes permanent disability or loss of movement and sensation below the site of the injury. The ability to control limbs depends on two factors: the neurological level of the injury, which is the lowest functioning segment of the spinal cord, and the completeness of the injury. An injury is considered complete if all sensory and motor function is lost below the neurological level. The injury is incomplete if there is still some sensory and motor function below the injury site. Symptoms of spinal cord injuries include loss of movement; loss of the ability to feel heat or cold; loss of touch; difficulty breathing; coughing; and loss of bowel or bladder control. (SOURCE: Mayo Clinic)

CAUSES: A traumatic blow to the spine that fractures, dislocates, crushes or compresses one or more of the vertebrae can cause a spinal cord injury. The nerve fibers that pass through the injured area are affected, and therefore, may impair part or all of the corresponding muscles and nerves below the site of the injury. Other causes of spinal cord injury include a gunshot or knife wound that penetrates and cuts the spinal cord. Arthritis, cancer, inflammation, infections, or disc degeneration of the spine can also cause spinal cord injury. (SOURCE: Mayo Clinic)

NEW SPINAL CORD INJURY THERAPY: The new therapy for spinal cord injuries uses oxygen deprivation in order to trigger molecular changes that excite or awaken the nervous system. The therapy uses acute intermittent hypoxia, which has its roots in sleep apnea studies. People with sleep apnea undergo short periods of oxygen deprivation, which stimulates spinal plasticity -- the ability of the brain and nervous system to respond to experience or injury. Intermittent hypoxia was tested on subjects who had been paralyzed, by placing a breathing mask on them that was connected to an air generator that stimulates the air at the peak of Mount McKinley then returns the air to normal. Nerve cells associated with voluntary leg strength were stimulated through a 30-minute mild oxygen deprivation session, resulting in improved ankle strength that lasted four hours.

FOR MORE INFORMATION, PLEASE CONTACT:
Lance M. Skelly
Director of Media Relations
Emory Hospitals and Wesley Woods Center Health Sciences Communications
(404) 686-8538
Lance.Skelly@emoryhealthcare.org

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THE FOLLOWING IS AN IN-DEPTH INTERVIEW WITH THE DOCTOR FROM THE STORY ABOVE:

Randy Trumbower, PhD, Assistant Professor, Rehabilitation Medicine Emory University School of Medicine, talks about a new way to help spinal injury patients.
What is this oxygen deprivation study, what is the idea here?
Dr. Trumbower: The concept of oxygen deprivation and as it applies to intervention for people with spinal cord injury is that we found from recent study in Chicago is that it actually enhances muscle strength for people that have had spinal cord injury.
What is going on in the body when you do that?
Dr. Trumbower: The concept actually started with some really fundamental studies that were first performed at the University of Wisconsin under the direction of Gordon Mitchell. And what they found was that by inducing low oxygen in animals or rats with spinal cord injury that their capacity to breath normally or voluntarily after the injury when given this low oxygen improved. So the idea with the intervention was to try to extend that to humans so the original set of data that we collected in Chicago was looking at applying a similar type of model in people that have had incomplete spinal injuries to see if it improves limb function.
What does the oxygen deprivation do to the spinal cord?
Dr. Trumbower: The idea that they studied in the animal models was looking at the molecular changes specifically looking at increases in specific proteins, key proteins that are involved in plasticity. Basically, when the spinal cord adapts to changes in environment and is able to take on new functions. And so these particular molecules brain drive neuro growth factors which are important for this adaptation became increased in concentration after the exposure to low oxygen.
How low is the oxygen and what effects are you hoping it’s going to have in human subjects?
Dr. Trumbower: In humans, what we’ve been doing is we’ve been depriving individuals with oxygen at between one and two minutes intermittently. So the exposure time would be approximately forty five minutes where they climb to Mt. Everest but not quite as high within a minute and a half and then they return to base camp. They do that intermittently for up to forty-five minutes.
How might that affect the spinal cord, what might that do that would help them?
Dr. Trumbower: So what we are trying to do is to repeat the animal model that was done which showed that intermittent exposure actually excites or primes the nervous system. Excites and wakes up the nervous system. And so what we’re hoping is that by intermittently stimulating the spinal cord with this type of breathing intervention that we’re actually turning up the volume on spare connections within the spinal cord. By doing that then those connections that were either dormant or turned off, are now excited. We can then begin to provide better connections between the brain and the muscles.
How would that translate in to quality of life improvement?
Dr. Trumbower: From our original study by actually turning up the volume on these connections we’re actually able to allow individuals with incomplete spinal injuries to use muscles that they weren’t able to use before. And weren’t able to use at a capacity that they were able to use before. And so from our first line of work, Proof of Principle paper that just came out, we found that individuals that experienced intermittent hypoxia for one day, so forty five minutes of exposure actually increased on average eighty percent changes in strength.
So this might help these patients have more motor function?
Dr. Trumbower: That’s right. So we looked particularly at ankle function which is if you think about when you walk fifty percent of the time that you’re walking involves the muscles in the back of your ankle, your calf muscles. What we found from the population thirteen individuals that we tested that their ability to contract that muscle voluntarily improved significantly. And so it’s reasonable to suggest that their ability to contract that muscle and to generate more strength would transfer to their ability to walk better so that’s where we’re going next.
Could this be part of a bigger picture in terms of a new kind of rehab for these kinds of patients?
Dr. Trumbower: Exactly. So what I envision and what my colleagues in Chicago and in Canada and also in Wisconsin envision is that this would be potentially a primer to traditional therapeutic interventions. Using this intervention as a way to excite the nervous system, wake it up and then couple it with traditional therapy such as gate training or a mass practice of the limbs that we want to focus on.
How many patients in this trial?
Dr. Trumbower: We’re trying to recruit forty individuals and so we started the trial last year and so far from the paper that I published this early spring we had thirteen individuals and now we are just starting the clinical trial.
How long will you follow them?
Dr. Trumbower: We’ll follow them out through two years.
What’s an incomplete spinal cord injury?
Dr. Trumbower: Incomplete spinal cord injury is an injury that involves partial sparing of certain connections within the spinal cord that more or less allow individuals to do more when they have an incomplete injury versus when they don’t.
The goal for these patients therapeutically is what then?
Dr. Trumbower: The ultimate goal is to restore function. And so one of the things that drives home to me as a clinician is to come up with novel strategies that will allow us to control the restoration of limb function. Control the ability to regain function and independence.
Is there anything important to add?
Dr. Trumbower: I think the important thing is that this is not an individual lab it’s a team. And it involves people here and at Emory University and at the Sheppard Center. We are working with some of the most prominent rehab centers in the country, the Sheppard Center and Center for Rehabilitation Medicine , and the Rehabilitation Institute in Chicago being the number one rehab center in the country that’s also teaming up with us to look at where we can take this. Really what’s wonderful about this study is its bench to bedside. That we’re doing this study in humans at the same time as the same work is being done in animals and really looking at the immunohistochemistry and the molecular changes that are occurring at the animal level. As well as what’s happening behaviorally in humans.


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